DIKE ENGINEERING - Introduction to Soft Soil Geotechnique: Content, Context and Application - page 304

condition and the minimum condition requested. The important question is how the
system will behave until the next moment of inspection.

inundation inundation Disaster Disaster

Threat Threat

breach breach

Failure Failure

slide slide

Mechanism Mechanism

erosion erosion settlement settlement

Consequence Consequence

overtoppping overtoppping leakage leakage piping piping uplift uplift liquefaction liquefaction compaction compaction

high waves high waves high waters high waters

Extreme event Extreme event

Counter
measures

Counter
measures

yes yes dike maintenance dike maintenance no no

Initiating
events

Initiating
events

waves waves settlements settlements earthquakes earthquakes human activities human activities

Figure 17.5 Event tree for flooding

principal limit states

principal element link

overtopping

height

wave overtopping
erosion outer slope

outer slope

instability outer slope
leakage

core

settlement
erosion inner slope

inner slope

instability inner slope
uplift

subsoil

piping
Figure 17.6 Dike system; relation between functions and failure modes

The following steps are distinguished: determination of functional demands,
evaluation of the condition until the next inspection, comparison with the norms,
choice of measures, and optimisation. Therefore, besides the daily maintenance an
overall check, every 6 years according to the Water Retainment Act, leads to an
actual High Water Protection Program, which will be executed in the following 6
years. Important aspects in this procedure are the concept of fixed and variable
data, the degeneration model and the system of diagnosis. How to determine the
actual strength of an existing dike? Pilot studies have been performed to clarify the